It is often desirable to tightly seal various small liquid-containing vessels to allow handling without inadvertent spilling. This is particularly desirable with soft drink containers, cups or other beverage vessels used to contain drinks or other potable liquids. Similarly, the concept is also useful when applied to paints, chemicals or closely controlled liquids where spillage may create a safety, environmental or aesthetic problem.
It is particularly important to provide a tight seal of the liquid when the vessel is inadvertently moved, tipped or placed at rest, while flexibly permitting access to the liquid for pouring or refilling. It is also important to insure that any gaseous accumulation within the sealed vessel may readily escape without disturbing the contained liquid independent of whether the vessel is upright, upset or substantially tipped.
The known prior art attempts to provide a solution to this problem have met with little practical success. For example, various vessels have been designed with an extremely wide base and narrow neck, thereby lowering the center of gravity and providing a "tip-less" feature. Nonetheless, even if not "tipped" or upset, liquid is capable of escaping through the open top of these types of vessels.
Attempts have also been made in the prior art to provide for mechanical-type lids having various mechanisms for opening and closing a pour spout in an effort to seal the underlying vessel. See, for example U.S. Pat. Nos. 4,183,443; 4,190,173; 4,276,992 and 4,303,173. These devices, however, have proven to be mechanically ineffective, unreliable and cumbersome and fail to address the problem of gaseous pressure buildup within the vessel attendant to tight sealing. Accordingly, these devices would not be amenable for use with liquids or other viscous materials that may present gases depending upon environmental conditions. Too, these prior art devices generally fail to include optimal conditions for pouring by the inclusion of a pressure equalization method, e.g., companion orifices for balancing inner and outer pressures. Thus, the prior art, although providing a sealed container, fails to address the more practical aspects presented by the problem of sealing and pouring.
Accordingly, the present invention contemplates a mechanically uncomplicated sealing mechanism adaptable for use with typical hand-held containers for tightly sealing and "spill-proofing" the contained liquid, while permitting easy access for pouring and refilling and an effective escape mechanism for potentially disruptive gaseous pressure buildup within the vessel. Thus, the present invention effectively and completely solves the problems prevalent in the prior art in an efficient, straightforward and mechanically practical manner.